Applications of electrical power began in the early 19th century after Michael Faraday, a British physicist, discovered the phenomenon of electromagnetic induction. Up to the late 19th century, various machines, such as the electrical generator produced by Siemens (a German engineer) and the electrical motor invented by Gelam (a Belgian engineer), were gradually developed with the principles of electromagnetic induction, and thus opened the age of machines driven by electrical power.
Electricity has become the most stable and convenient energy that people relies on in daily life. Motors can convert electrical power into mechanical power. As technology advances, the application scope of motor increases. According to a report of International Energy Agency, the electrical consumption of motors and motor-driven equipment occupies nearly half of the global electrical consumption.
In recent years, application of motors focuses on electrical vehicles, the technology of which was researched and used in the middle or later period of 19th century due to easy operation of electrical vehicles. However, due to vehicles of combustion engine advancing in technology more than electrical vehicles, except some electrical vehicles designed for specific purposes, most of electrical vehicles disappeared from the market upon the advent of the 20th century. In the late 20th century, due to the issues of environmental protection and oil crisis, vehicles using fossil fuels are subjected to a great impact. When renewable energy is considered to replace fossil fuels, electrical vehicles using clean energy are under attention. Alternatively, hybrid vehicles are another option for replacing oil-driven vehicles.
According to the experience of developing electrical vehicles, the battery technology occupies about 20-50% of the total cost, and the driving system technology occupies about 10-20% of the total cost. This implies that the driving system will play an important role on the development of electrical vehicles. For an electrical vehicle, the driving system is generally comprised of a motor, a controller, and an inverter/converter. For ease of illustrating the following paragraphs, the controller, inverter, and converter for the driving system of an electrical vehicle are referred to as “control circuits”, which can be used in combination by those skilled in the relevant art for satisfying the requirement of an application.
Since the driving system of an electrical vehicle can only use the limited energy stored in the battery, for providing an adequate force for moving the body of the electrical vehicle and allowing the electrical vehicle to have an adequate endurance capacity, an efficient high-voltage AC motor has to be employed. However, an AC motor would generate a lot of heat when converting electrical energy into mechanical energy. In addition, a control circuit would generate a lot of heat when converting a low-voltage direct current, which is supplied from a battery, into a high-voltage alternate current for an AC motor. For a hybrid car or an electrical motorcycle, due to the waste heat generated from operation of the motor or reverse recovery of kinematic energy, the performance and safety of the car or the motorcycle can be influenced. Thus, it is an important topic for a manufacturer of electrical vehicle to develop a vehicle that can effectively dissipate the heat generated in its driving system to reduce the temperature within the vehicle and thus to ensure the driving system to work at a proper temperature.
For easy of illustrating the dissipation problem existing in electrical vehicles, a typical model of a driving system 9 commonly used in a commercial electrical car is shown in FIG. 1. In the driving system 9 of the electrical car, the motor 91 and the control device 93 are made in separate modules and located in different locations, wherein leads 95 are electrically connected between the control device 93 and the motor 91. Furthermore, a cooling device 97 is employed to work with a motor heat sink 971 at the motor 91, and to work with a controller heat sink 973 at the control device 93. However, the driving system 9 is complicated in structure and occupies a lot of space, and this may cause difficulty in assembling components or conducting maintenance and increase the cost. Besides, due to the electrical car consuming a lot of electrical energy, which may range from more than ten kilowatts to several megawatts, and the fact that the electrical leads connected between the power source, the control circuit, and the motor are run through several connection terminals along entire length of the electrical leads, in case one of the connection terminals is loosed or corroded, heat can be released and thus may cause a risk to the electrical car.
In an electrical vehicle, since a motor thereof usually has a cylindrical housing and is provided with an output shaft extending along a central axis between the stators located in the housing, two bearings are required to be respectively installed at the front end and the rear end of the housing to ensure smooth operation of the output shaft. Some manufacturers attempted to locate the control circuit as close to the motor as possible for reducing the electrical transmission loss and saving the space. However, for a water-cooled motor, the locations of the water inlet and the water outlet should be considered carefully to prevent them from interfering with the output shaft of the motor, so that the space can be saved, the structure can be simplified, the efficiency of thermal conduction can be increased, and the length of the electrical leads can be reduced.
In view of the foregoing, the present invention intends to introduce an effective way for dissipating the heat generated in an electrical vehicle, which usually has a limited space, so that the probability of an accident can be reduced, components can be assembled more easily, maintenance can be conducted more easily, and the manufacturing cost can be reduced.